Heretofore, there have been many difficulties and inconveniences in the process of transplanting human organs from one person to another. For example, patients waiting to receive an unrelated donor kidney have to be on constant standby in the hospital, sometimes for weeks. When the donor appeared, the timing was very important, for the surgery had to be substantially simultaneous so that immediately upon removal of the kidney from the donor, it could be transplanted into the patient. This meant that there had to be at least two surgical teams working on the transplantation. The donor and the patient had to be located very close to each other during these operations, because there was no practical way of preserving the kidneys for any substantial period of time after they had been removed from the donor body and before they were transplanted into the patient's body. The procedure was always therefore an emergency procedure and was fraught with risks as well as difficulties. Similar problems and the same difficulties have applied to the transplantation of other organs, such as a heart or liver.
It has always been a goal in the preservation of human organs to make it possible to keep the organ alive for many hours and up to several days after harvesting the organ from the donor body. This would make it possible to use cadaver's kidneys, hearts, and livers and to have the harvesting operation and the transplant operation spaced apart by several days. The transplantation, therefore, could be an elective rather than an emergency procedure. Since additional time could be available, it would become possible to match the donor and recipient by tissue typing; unrelated donors who have proved compatible by tissue typing are generally as successful as donors who are related to the recipient. If additional time were available, and the organ could be preserved for a longer period of time, it would become possible for the recipient to wait at home until the correctly matched kidney or kidneys would become available. Furthermore, extra time would enable a single team of surgeons to do the harvesting operation and the transplanting operation. The surgery could be spaced apart by several days if necessary. Alternatively, the use of two teams could still be possible, but they would not need to be as close to each other at the time, for the organ to be transported substantial distances during the preservation time when the organ is being perfused outside of the body prior to transplanting.
Previously, organs have been transported from the donor to the recipient by the use of common ice coolers. The organ is placed into static cold storage and delivered by hand from one hospital to another. The use of common ice coolers was developed because of the convenience of finding packaged ice at locations remote from the hospital. Unfortunately, the transport of kidneys in static cold storage has resulted in problems. Typically, intercellular acidosis will occur. Intercellular acidosis is the build-up of acids and other toxins in the organ. Eventually, these toxins will damage or destroy the organ. Another problem is the inducement of hypothermia into the stored organ. Over a period of time, the cold static storage may cause the organ cells to begin swelling and cause eventual failure. Acute tubular necrosis, or post transplant early organ dysfunction, occurs much more frequently in patients where the kidney is placed in static cold storage, causing the patient to require post transplant dialysis. As such, over the years, it was determined that pulsatile pumping action is necessary to maintain organ viability so as to preserve the organ for a longer period of time.
U.S. Pat. Nos. 3,632,473 and 3,753,865 issued to Folkert O. Belzer et al. Dr. Belzer was an early pioneer in preservation technology for effectively storing human organs. These patents describe a system that incorporates the transfer of organs, such as kidneys, hearts, livers or other organs from the donor's body into a perfusion chamber where human plasma, kept in constant supply and preferably fortified with hormones and other substances, as pumped through the organ. In the perfusion chamber, the organ functions generally as it would in the body. For example, the kidneys in the perfusion chamber produce urine. The system maintained the organ at low temperatures so that the organ's activity is kept at a minimum. The plasma, which is circulated through the organ, is recirculated and oxygenated. The pH of the plasma is adjusted by a supply of carbon dioxide. Dr. Belzer's system utilized careful filtering so as to enable the plasma to be kept free from foreign matter.
In Belzer's system, the pumping of the plasma through the organ is done by pulsatile pump such that pulses similar to those produced by the human heart are employed to force the cold plasma through the organ. Pressure is controlled with the aid of a damper having an air spring. The operation of the apparatus thus resembles the operation in the human body, but differs in the fact that it is being conducted at a very low temperature and in a type of controlled environment. In Belzer's system, in the transport and storage of kidneys, for example, it was not necessary to free the recirculated plasma from the small amount of urine produced during storage, for the freeing of the kidney from the urine can take place later in the patient's body after transplant. Pressures maintained on the organ are substantially those encountered by the organ in the human body. The flow of plasma through the organ is controlled in accordance with the pressure desired. In particular, the Belzer system utilized an air trap and the monitoring of the gauge pressures within the air trap so as to provide an indication of fluid pressure.
Another system that has been used for the preservation of organs during transportation is identified as a "MOX-100 Renal Preservation System" and is sold by Waters Instruments, Inc. of Rochester, Minn. This system was designed to provide long term, unattended perfusion of one or two kidneys in the hospital or in the operating room. This device utilizes a disposable cassette for organ storage which is molded and placed within the system. The cassette provides membrane oxidation with a static membrane and gravity perfusate flow of up to 600 milliliters per minute. A complete circulatory system is provided including an arterial reservoir, a pump head, a heat exchanger, a bubble trap, a venous reservoir, a plasma flow meter, and a membrane oxygenating sack. The overall system connects the pulsatile pump chamber and gas and refrigeration sources to this cassette. The system includes visual and audio alarm systems which indicate pressure or temperature problems or input power failures.
In Belzer's system and in Water's system, the fluid pressure to the organ is delivered mechanically. Additionally, each system utilizes a bubble trap so as to remove bubbles and gases from the organ preservation fluid. As a result, fluid pressure is measured from the bubble trap which contains air as well as solution. As such, the pressure was not a true blood pressure, but rather a gauge pressure which is dampened by the air in the bubble trap. It has been a common problem that both the Belzer system and the Waters system would occasionally damage the organ by over perfusing, causing irreparable damage by the application of pressures that were too great. There are no monitoring devices or safety devices to prevent the application of improper fluid pressure. Also, neither the Belzer or Waters system provides true dicrotic pulsatile action to the organ. As a result, accurate simulation of the human heart action was not accomplished by either of these systems.
It is an object of the present invention to provide a human organ preservation apparatus that effectively preserves the life of the organ outside of the human body.
It is a further object of the present invention to provide an human organ preservation apparatus that has the ability to salvage organs from non-heart beating donors.
It is a further object of the present invention to provide a human organ preservation apparatus that effectively monitors diastolic and systolic pressures effecting the organ.
It is another object of the present invention to provide a human organ preservation apparatus that effectively simulates dicrotic heart pumping action.
It is another object of the present invention to provide a human organ preservation apparatus that maintains the organ in a cold environment.
It is a further object of the present invention to provide a human organ preservation apparatus that simplifies monitoring and control requirements.
It is still a further object of the present invention to provide a human organ preservation apparatus that provides a continuous and uninterrupted fluid flow from the pulsatile pump to the organ.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specifications and appended claims.